In a conventional direct current motor, a permanent magnet mounted on a stator establishes a stationary magnetic field. A rotor that turns within the field carries a segmented electrical winding. As the rotor turns, the winding segments interact with a commutator so that the direction of current flow in each segment is reversed as it reaches a switch-over position. At any given time, the current flow in the various segments is such that the electromotive forces applied to them are cumulative to urge the rotor in a particular rotational direction.
The direction in which the rotor turns is thus determined in accordance with Lenz's law, by (1) the direction of current flow in the winding segments, i.e., the commutator orientation and (2) the direction of the magnetic field. Reversal of the motion of the rotor can be accomplished by switching the electrical connections of the commutator to reverse the current direction corresponding to each winding segment position. This commutator principle is employed in a similar manner in direct current generators.
An objective of the present invention is to provide an improved motor or generator in which the direction of rotation can be reversed without any electrical switching. A further objective is to provide such a motor or generator that is of simple reliable construction with a minimum of movable parts and without a complex magnetic circuit.